Note: Frames refer to frames of game logic. To put things in perspective, the game logic is designed to run 60 times per second. Think of them as 'tics'

SETV d0,100

This sets the d0 register to 100. Tis is a counter used to determine how long the ff combo should move for in frames (as I'll explain below)

SETV xd,1
SETV yd,1

Sets the X speed and the Y speed to 1 pixel and1 pixel respectively. This makes the platform move diagnoally lright-down.

WAITFRAME

Lemme explain this a bit further (ignore the (1) for now. When a script executes, it continues executing instructions indefinitely until 1 of three things are found 1) a QUIT statement. 2) The end of a script, and 3) a WAITFRAME statement. What this basically means is that the script stops executing for that particular frame. In the next frame of game logic, the script will resume execution from the satement AFTER the WAITFRAME statement.

SUBV d0,1

Subtracts 1 from the d0 register and puts the result into d0. So, it starts at 100, so thisdecrements it by 1.

COMPAREV d0,0

Checks to see if d0 is equal to 0. Since it's not equal, the TRUEFLAG (an internal flag used by the scripts) is not set. BTW, since d0 is 99 right now, and 99 >= 0, the MOREFLAG will be set, but that's not important right now.

GOTOTRUE 9
GOTO 4

GOTOTRUE will go to the instruction number listed if the TRUEFLAG (described above) is set. Since it isn't set, it will simply skip over this instruction. GOTO goes to the instruction number regardless of anything else. So basically, the logic of this function decrements d0 by 1 every frame (instruction 4 is WAITFRAME, so it jumps to this) until d0 is 0. During this time, the platform moves 1 pixel down and 1 pixel right every frame. When d0 is 0, the TRUEFLAG is set, and GOTOTRUE executes, going to instruction 9 (see below).

SETV d0,100 ; Instruction 9
SETV xd,-1
SETV yd,-1
WAITFRAME ; Instruction 12
SUBV d0,1
COMPAREV d0,0
GOTOTRUE 1
GOTO 12

Now we can figure out the logic of this statement. d0 is set to 100 initially again, and the x accel and y accel values are reversed to -1 and -1 repectvely. Then, a WAITFRAME is read, and on the next frame, it decrements d0 by 1, checks if d0 is equal to 0, then jumps to instruction 1 if it is zero, thus restarting the script. Otherwise, it jumps to instruction 12, where it WAITFRAMES, decrements d0 again, and checks for 0 again. When 0 is reached, z accel and y accel are set to 1,1 again. Thus, the ff combo moves diagnoally right-down for 100 frames, then up-left for 100 frames, repeat ad infinium.

Hope that isnt too hard to understand.